Various medical instruments may be used in connection with an endoscope for performing a number of operations at a site deep within a patient's body cavity. One such instrument, a biopsy forceps device, samples tissue from a body cavity with minimal intervention and discomfort to patients. Typically, a biopsy forceps device, like other endoscopic instruments, has a long flexible tubular member for insertion into a lumen of an endoscope. The tubular member is sufficiently long and flexible to follow a long, winding path of the body cavity. An end effector assembly, such as a biopsy forceps assembly, is attached at a distal end of the tubular member, and a handle is attached at a proximal end of the tubular member. An elongate mechanism, such as a pull wire, extends through the tubular member to connect the end effector assembly and the handle. A biopsy forceps assembly, for example, may include mating jaws actuated by the handle to sample a body tissue.
There are numerous types of endoscopic medical intruments in use today. These instruments have various actuator/end effector assemblies and connections configured to provide certain benefits. For example, one type of endoscopic medical instrument includes a single, elongate flexible pull wire extending through the instrument and connected at its distal end to a relatively rigid actuator having an axis along the instrument. That actuator includes a pair of pins at one end, each pin supporting an end of one link. The other end of each link connects to a jaw. A support pin supports the jaw assembly. This assembly can generate a relatively large closing force at the jaw assembly. The jaws of the jaw assembly pivot together about the support pin because they are connected to a single actuator. This limits the range of rotation of the jaws.
Another type of endoscopic medical instrument includes a pair of elongate, flexible pull wires extending through the instrument. Each wire connects at its distal end directly to a lever arm of a jaw. In this configuration, each jaw is supported on and pivots about a single pivot pin. With this assembly, as the wires are pulled proximally to close the jaws, the torque about the pivot pin decreases, thereby decreasing the closing force.
A further endoscopic medical instrument includes a jaw assembly with a pair of jaws connected to a pair of arms extending from a jaw housing. Each jaw has a shank that has a surface facing a surface on corresponding arms. A cam slot on each jaw shank is slidably engaged by a cam pin on the arms. A puller member axially movable within the housing supports a pair of pivots, each of which pivotally engages a jaw shank. The puller member is attached to a drive wire coaxially positioned in a tubular shaft such that axial movement of the drive wire actuates the puller member. In response to axial movement of the puller, the cam pins riding in the cam guide slots change the position relative to the fixed jaw pivot axis of the jaw, thus actuating the jaws.
Another endoscopic medical instrument includes a single flexible pull wire that connects at its distal end to a relatively short rigid tube. The tube extends over and moves axially relative to the jaw assembly to close the jaws.